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This invention relates to methods of preparation of energetic salts, particularly of triazole (or triazolium) salts and the resulting salts.
Presently, hydrazine is used in propellant scenarios, whether as a boost material or in altitude control devices. Hydrazine has several shortcomings, most which are inherent to the basic properties of the material. It has a relatively high vapor pressure at ambient temperature, 12-14 torr, which leads to vapor toxicological problems, and is also a known carcinogen. Its specific gravity is approximately 1.0 g/cm3 at ambient temperatures. All of these properties can be significantly improved upon, with the use of new materials in monopropellant formulations.
In the prior art are U.S. Pat. Nos. 5,274,105 and 5,256,792, which disclose new energetic salts of high nitrogen heterocycles based on 1,2,4-triazole. But none are seen as pertinent to the claimed compositions.
Accordingly there is need and market for energetic propellant ingredients, which are easily synthesized in high yields, and have reduced vapor pressures at ambient temperatures and otherwise overcome the above prior art shortcomings.
There has now been discovered energetic salts which have reduced vapor pressures at ambient temperatures, significantly higher densities than hydrazine, improved specific impulse values and thermal stability. Also such salts can be made from commercially available starting materials in high yields, as discussed below.
Broadly, the present invention provides, an inventive method for preparing energetic, triazole (or triazolium) salts comprising, reacting the following: 
where R and Rxe2x80x2 are H or NH2, except that when Rxe2x80x2=H, R=H; and X is NO3, ClO4xe2x88x92, or N(NO2)2xe2x88x92.
The invention also includes the above resulting salts and will become more apparent from the following detailed specificaton:
The energetic triazole salts of the invention are based on three heterocycle systems, 4-amino-1,2,4-triazole, 3,4,5-triamino-1,2,4-triazole, and 1,2,4-triazole. Two of the heterocycle systems are well known materials from the literature. 4-amino-1,2,4-triazole is readily synthesized from formic acid and hydrazine in the presence of certain catalysts. (U.S. Pat. No. 5,099,028; Org. Synth. 1944, 24, 12). While 3,4,5-triamino-1,2,4-triazole is easily synthesized in high yield and purity from the reaction of equivalent amounts of hydrazine with dimethylcyanamide under heating (J. Heterocyc. Chem. 1965, 2, 98). 1,2,4-triazole is commercially available. Once formed, these heterocycles can be reacted in a single reaction, in commonly available solvents, to form highly energetic salts of interest. The reaction is as follows.
[Heterocycle]+HXxe2x86x92[HeterocycleH+][Xxe2x88x92]
where HX=HNO3, HClO4 or HN(NO2)2 
In the above reaction, the heterocycle acts a proton acceptor from the strong acid HX. Once protonated, the heterocycle, [Heterocycle H+], then pairs with the corresponding anion, Xxe2x88x92, to form a neutral salt which can be isolated as a pure material. The formed salts are stable materials with excellent thermal stability at elevated temperatures, and have desirable safety properties (impact and friction insensitivity).
1,2,4-triazole is commercially available. The other two triazole materials are readily available from one-step, high yield processes That is, 4-amino-1,2,4-triazole, which is a white crystalline, air-stable solid, with a melting point of 85xc2x0 C., was synthesized readily from formic acid and hydrazine at elevated temperatures in the presence of an acid catalyst. (U.S. Pat. No. 5,099,028) (Reaction 1). 
While 3,4,5-triamino-1,2,4-triazole, a white solid with a melting point of 254xc2x0 C., was readily synthesized by heating equal amounts of dimethylcyanamide and hydrazine (J. Heterocyc. Chem. 1965, 2, 98) (Reaction 2). 
Energetic 4-amino-1,2,4-triazolium salts were synthesized in dry methanol, from reaction of the heterocycle with the desired form of the strong acid. All salts were formed in nearly quantitative yield and high purity (Reaction 3). 
where Hxe2x80x94X=HNO3, HClO4, or Hxe2x80x94N(NO2)2.
For the synthesis of the nitrate and perchlorate salts, the concentrated, aqueous solutions of both acids, were used. For the synthesis of the dinitramide salt, since free dinitramine is known to be extremely explosive, the use of a strongly acidic, cation exchange resin bed was employed. Ammonium dinitramide, the starting material, was dissolved in anhydrous methanol, then eluted through the strong cation exchange resin, and into a methanol solution of 4-amino-1,2,4-triazole.
All of the resultant salts of 4-amino-1,2,4-triazole have lower melting points than that of the starting heterocycle. The nitrate salt melted at 68xc2x0 C., the perchlorate salt at 73xc2x0 C., and the dinitramide salt melted at around 20xc2x0 C. Both the nitrate and perchlorate salts of 4-amino-1,2,4-triazole were white crystalline solids. The dinitramide salt could not be made crystalline. However DSC studies of the dinitramide salt, revealed an endotherm indicative of a melt, at +20xc2x0 C.
Synthetic endeavors with 3,4,5-triamino-1,2,4-triazole were similar to those involving the previous heterocycle, 4-amino-1,2,4-triazole (Reaction 4). The reaction was significantly slower, due to the poor solubility of the parent heterocycle in polar solvents. 
where Hxe2x80x94X=HNO3, HClO4, or Hxe2x80x94N(NO2)2 
Upon completion of the reaction simple removal of the solvent by high vacuum, left highly crystalline, non-solvated salts. All of the product salts have relatively high melting points, the nitrate salt melted at 205xc2x0 C., the perchlorate salt at 196xc2x0 C., and the dinitramide salt melted at 145xc2x0 C. The nitrate and dinitramide salts"" melting points are impressive. Examples for comparison, include, guanidinium nitrate melt point of 214xc2x0 C., while ammonium nitrate melts at 169xc2x0 C. (Explosives, 4th Edition, VCH Germany, 1993). Ammonium dinitramide melts at 92xc2x0 C., but doesn""t decompose until 135xc2x0 C. (U.S. Pat. No. 5,254,324).
The synthesis of the 1,2,4-triazole salts is identical to that of the 4-amino-1,2,4-triazole family (Reaction 5). 
where Hxe2x80x94X=HNO3, HClO4, or Hxe2x80x94N(NO2)2.
The product 1,2,4-triazolium nitrate, was a white crystalline solid with a melting point of 137xc2x0 C., while the perchlorate salt had much lower melting point of 89xc2x0 C. The dinitramide salt was a white crystalline solid with a melting point of 75xc2x0 C.